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Mally

Is it true that you can tell the age of the universe by measuring the redshift of light?

  • 2 years ago
  • 2 years ago

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  1. antrio
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    no sure....but the red shift phenomenon is a well established proof for that the universe is expanding....

    • 2 years ago
  2. Mashy
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    yea red shift is basically doppler shift!.. which happens in all waves!

    • 2 years ago
  3. Mally
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    I'm not very informed on this topic lol, would you mind giving me a few more details?

    • 2 years ago
  4. Mashy
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    ok, doppler shift is a phenomenon, which we experience in our daily lives, for example when a speeding vehicle making a siren passes by you, you hear that change in the frequency..it feels like as the vehicle is nearing you, the frequency increases (becomes squeakier) and as it moves away from you.. its frequency decreases!.... so that happens in light waves as well.. so since.. we see that the wavelength of light is becoming red.. which means frequency is decreasing (light which we see from stars)..! thus, the stars are moving away from us, hence universe is expanding!

    • 2 years ago
  5. Mashy
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    sorry my explanation is not all that formal :D!..

    • 2 years ago
  6. Mally
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    No, it's great! A lot easier in this form than had you dressed it up in its jargon dress. Is this an accurate way of measuring the age of the universe though?

    • 2 years ago
  7. Mashy
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    ermm.. even I dunno if thats how the age of the Universe is measured.. but i think, by finding out at what speed exactly the galaxies and the stars are moving away from us, and by retracing it Backwards.. we could be able to guess the age.. but then again.. m not very sure :D.. we we know its 13.7 billion years old though :D!

    • 2 years ago
  8. Carl_Pham
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    Not alone, no, but in combination with other measurements, yes. Light is redshifted when the emitter is moving away from the observer. You can measure the redshift in thel ight emitted by a distant galaxy by looking for the characteristic ("signature") pattern of emission lines of some element, for example hot hydrogen. If the galaxy is moving away from us, the pattern will appear at a lower frequency (towards the red end of the spectrum) than it does in the lab. Measuring the redshift and applying a formula from special relativity will tell you the velocity of the distance galaxy, relative to us. Now you need some indepenent measure of the distance of the galaxy. One possibility is measuring the brightness of a star that has some theoretical value of its absolute brightness. Certain variable stars, for example, have a reliable correlation between their period (how often they brighten and dim) and how bright they are. You look for one of these variable stars, measure its period and its apparent brightness. The period tells you its absolute brightness (how bright it would be if it was at some standard distance, say one light-year, from us). By comparing this to how bright it actually appears, you can deduce how far away it is, and hence how far away the galaxy is. Now that you know the velocity of the distant galaxy and its distance, you can calculate how long ago that galaxy was right next to ours. That's a reasonable approximation to the age of the universe, if you assume everything started ouit as one big glob.

    • 2 years ago
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